The European Union health commissioner suggested that Europeans avoid nonessential travel both to Mexico and parts of the United States. Russia, Hong Kong and Taiwan said they would quarantine visitors showing symptoms of the virus. Mexico, where the number of deaths believed caused by swine flu rose by 50 percent on Monday to 152, is suspected to be ground zero of the outbreak. But Mexican Health Secretary Jose Angel Cordova late Monday said no one knows where the outbreak began, and implied it may have started in the U.S. "I think it is very risky to say, or want to say, what the point of origin or dissemination of it is, given that there had already been cases reported in southern California and Texas," Cordova told a press conference. It's still not clear when the first case occurred, making it impossible thus far to determine where the breakout started.

Dr. Nancy Cox of the Atlanta-based Centers for Disease Control and Prevention has said she believes the earliest onset of swine flu in the United States happened on March 28. Cordova said a sample taken from a 4-year-old boy in Mexico's Veracruz state in early April tested positive for swine flu. However, it is not known when the boy, who later recovered, became infected. The World Health Organization raised the alert level to Phase 4, meaning there is sustained human-to-human transmission of the virus causing outbreaks in at least one country. Monday was the first time it has ever been raised above Phase 3. Putting an alert at Phases 4 or 5 signals that the virus is becoming increasingly adept at spreading among humans. Phase 6 is for a full-blown pandemic, characterized by outbreaks in at least two regions of the world.

Fifty cases - none fatal and most of them mild - were confirmed in the United States. Worldwide there were 79 confirmed cases, including six in Canada, one in Spain and two in Scotland. Thirteen are suspected in New Zealand, and one is suspected in both France and Israel. Symptoms include a fever of more than 100, coughing, joint aches, severe headache and, in some cases, vomiting and diarrhea.

Amid the alarm, there was a spot of good news. The number of new cases reported by Mexico's largest government hospitals has been declining the past three days, Cordova said, from 141 on Saturday to 119 on Sunday and 110 Monday. In a bid to prevent mass contagion, Mexico canceled school nationwide until May 6, and the Mexico City government is considering a complete shutdown, including all public transportation. The Cinco de Mayo parade celebrating Mexico's defeat of a French army on May 5, 1862 and Mexico City's traditional May 1 parade were canceled. More than 100 museums nationwide were closed.

The Tamil Tigers are now defending their jungle bases

Mullaitivu was not only the last major rebel-held town in the north-east but also acted a crucial military supply base.

"The LTTE's main supply route, especially military equipment and hardware, were supplied through Mullaitivu," Dharmalingam Siddarthan, a former Tamil militant turned politician, told the BBC.

Sri Lanka's government is confident of victory in the war, which began a quarter of a century ago. Some officials have predicted the army will completely recapture the north from the Tamil Tigers in the coming weeks.

So, why are the Sri Lankan forces winning now?

The political leadership is strongly backing the military, which has nearly doubled its numbers in recent years. The government has also increased the firepower of security forces by buying new arms from Pakistan and China.

In addition to this, the army has changed its tactics and become better able to cope with the kind of warfare waged by the guerrillas. It also started to stretch them thin by opening up a number of fronts in the north.

However, many military analysts believe that the army may need thousands of additional soldiers to hold on to the territory it had recaptured from the rebels in the long-run.

The Tigers have shown resilience in the past and with most of their heavy weapons and cadres intact, they may spring a surprise. Even if the rebels lose control of other smaller towns and villages in the remaining areas, they may revert back to guerrilla warfare.

The rebels insist Velupillai Prabhakaran is still leading their fight

Sri Lankan officials think he may have fled the country.

But speaking to the BBC Sinhala service, senior rebel leader B Nadesan said it was nothing but malicious propaganda and their leader was very much within the north-east leading the movement.

He also shrugged off recent military setbacks saying "in the past we have withdrawn many times and bounced back to achieve big victories".

Many Tamils here warn that the capture of territory from the rebels alone will not end the ethnic conflict and that they need a political solution for a lasting peace.

"Everything depends on the government. If it fails to devolve powers to the Tamil-dominated north and east after sometime the same problem will come up again," warns Mr Siddharthan.

But the Sri Lankan government says it is working on a political solution and it requires time to evolve a consensus among political parties in the south.

"The political solution is evolving as we watch in Eastern province. We've had elections and had a chief minister, who's a Tamil and a former child solider being elected to office. This is part of the political process," says Sri Lankan Foreign Secretary Palitha Kohonna.

"If anybody were to expect the revelation of a political solution in one morning it is not going to happen like that. It will happen slowly. It will be an evolution rather than a sudden declaration," says Dr Kohonna.